This invention pertains to apparatus and methods for in-space satellite operations, such as modifying the useful life of a space satellite, inspecting it, adjusting its space trajectory, and the like.
More particularly, the invention relates to such apparatus and methods for extending or otherwise modifying the useful operational lifetime of satellites which perform communications, weather reconnaissance, space reconnaissance and similar functions.
In another respect, the invention pertains to such apparatus and methods for extending the useful life of such satellites without performing complicated in-space refueling or repair functions.
According to still another aspect, the invention pertains to apparatus and methods for effecting planned deorbit and reentry of a satellite or reboosting a spent satellite to a higher orbit or another trajectory, to delay deorbit or to place a satellite in a parking or other operational or non-operational orbit or trajectory. Similarly, the invention relates to effecting the deorbit or altering the trajectory of debris in space to avoid collisions with other spacecraft.
In yet another aspect, the invention pertains to apparatus and methods for performing a variety of proximity operations, e.g., inspection of an operational or non-operational satellite, to determine its status, etc.
In still another aspect, the invention pertains to apparatus and methods for delivering or replenishing supplies to orbiting spacecraft such as the planned International Space Station.
Because of the high reliability of contemporary electronics, the end-of-life (EOL) of most satellites is caused by on board propellant depletion and the corresponding loss of attitude and position control, i.e., for orientation, pointing, including stabilization, and orbit control. The previous proposed approach to extending EOL is to replenish the propellant in the satellite tanks by refueling from another spacecraft. Alternatively, mechanical attachment of additional external propellant tanks to the target satellite would also accomplish this objective.
In addition to EOL by normal propellant depletion, there have been numerous instances in which satellites have been initially delivered to unacceptable orbits. These orbits have been corrected by additional propulsion maneuvers. However, use of the satellites' onboard propellant to move it to an acceptable orbit resulted in a corresponding reduction in the useful life of the satellite. In some instances, initial orbit correction was impossible because it would have completely depleted the satellite's onboard propellant supply.
In the past, considerable effort has been expended to develop in-space refueling technology. However, this has required extensive and expensive modifications to conventional satellites, risky proximity operations, possible contamination of the satellite by escaping fuel and other practical problems.
Conversely, when extension of the operating life of a satellite cannot be effected for various reasons, e.g., other malfunctions of a satellite or its equipment which cannot be repaired or obsolescence of the satellite, it would be desirable to be able to effect pre-planned deorbit and reentry. In this way, the inoperable or obsolescent satellite will not continue to clutter the available space for working satellites and reduce the likelihood of collision with other satellites or space vehicles. If the deorbit and reentry can be preplanned, these techniques will also reduce the possibility of reentry into populated areas with possible disastrous results. Furthermore, even if planned deorbit and reentry is not necessary or if it would be desirable to otherwise change the space trajectory of a satellite, it would be desirable to provide apparatus and methods for changing the space trajectory of a satellite to another operational or non-operational trajectory or for reboosting satellites which are cluttering useful orbits or which are about to deorbit, into less cluttered and less dangerous parking orbits.